DETROIT — The Jets’ defensive line is filled with first-round picks, but the man in the middle tonight against the Lions in the first preseason game will be Kenrick Ellis, the third-year player from Hampton, who seems to be hitting his stride.

Ellis does not have the high profile of Muhammad Wilkerson, Quinton Coples or Sheldon Richardson, the first-round crew, but his role is just as important. Ellis, a third-round pick in 2011, is the starting nose tackle, replacing Sione Po’uha. The Jets’ run defense was a weakness last year. Ellis hopes to be a big part of changing that.

Ellis has had some good moments in training camp, and he said he feels comfortable in the system entering Year 3.

“It’s just night and day,” he said. “In the grand scheme of things, I know where I need to be and I know how to get there now. I try not to make any mental mistakes and I try to be as physical as possible. It’s second nature now. It’s less thinking and more reacting.”

The Jets let Po’uha go as a cap casualty and allowed defensive tackle Mike DeVito to walk in free agency. That has left a bunch of young pups to play in the defensive front.

“We have some great vet guys that left, but it’s just an opportunity for some young guys to step up and fill that void,” Ellis said.

* Coach Rex Ryan grew annoyed Wednesday afternoon during the final practice before tonight’s game when rookie linebacker Troy Davis tackled tight end Chris Pantale in a non-contact drill. Ryan called Davis over and chewed him out, then said, “That’s it. Practice is over.”

“[Davis is] an aggressive guy and things like that,” Ryan said. “I think he’s just a young man like a lot of guys are trying to make an impact, make a name for himself and things like that … I can’t wait, I’m really excited to see him play [tonight] because he is a very physical, aggressive player and that’s great to see. The big message is just to make sure we’re taking care of each other, though.If it’s a live scrimmage situation, that’s great. If it’s not, we’ve got to practice like a pro. And sometimes, and not just picking on Troy, a young player sometimes you say it, and you say it but they need to understand that no, no it’s unacceptable.”